Study On The Phosphate Cement Repair Mortar Contains Circulating Fluidized Bed Ash

Phosphate cement repairing mortar has the advantages of high strength,fast hardening,strong cohesion,good volume stability.However,phosphate cement repairing mortar also has the shortcomings of fast setting time,intense hydration and exothermic heat release,and high price.These shortcomings limit its application.The research shows that circulating fluidized bed ash?CFB?can improve the early strength of slurry,reduce the hydration exothermic rate,improve the frost resistance,reduce the cost,and has a good effect of compensating shrinkage.Firstly,this paper analyses the influence of the ratio of raw materials on the basic properties of Magnesium phosphate cement?MPC?,optimizes the mix ratio parameters by the efficiency coefficient method,and explores the adaptability of common water reducing agents to MPC system.Secondly,the physical and chemical properties of CFB are analyzed,and the influence of CFB on the macroscopic properties of MPC such as workability and strength were explored.The influence of CFB on the hydration heat release rate and total amount of hydration heat release of MPC is analyzed.The morphology and hydration reaction mechanism of MPC system containing CFB are analyzed from the microscopic point of view.Finally,the influence of CFB on the compressive strength,interfacial flexural strength and bond pull-out strength of MPC repairing mortar is explored.The influence of CFB on the durability of MPC repairing mortar is analyzed comprehensively from the aspects of water resistance,frost resistance and volume stability.The results show that:?1?The different Mg/P ratio(m?M?/m?P?,B/Mg ratio(m?B?/m?M?,water-binder ratio(m?W?/m?MPC?have significant effects on the setting time,fluidity,1.5h compressive strength and 3d compressive strength of magnesium phosphate cement system.?2?The optimum mix ratio parameters of MPC obtained by efficacy coefficient method are m?M?/m?P?=3,m?B?/m?M?=0.12 and m?W?/m?MPC?=0.10.Calcium lignosulfonate?MG?,amino sulfonate water reducer?ASP?,naphthalene-based superplasticizer?FDN?,poly carboxylic acid superplasticizer?PC?have no obvious water reducing effect on MPC system,but the adaptability of MG and PC to MPC system is better than that of ASP and FDN.?3?CFB has strong water demand,self-hardening and high activity.With the increase of CFB content,the setting time of MPC system decreases,the fluidity of slurry decreases,and the compressive strength of slurry increases gradually at 1.5h;the hydration exothermic rate decreases obviously,and the total amount of hydration exothermic heat decreases;the production of MgKPO₄·6H₂O decreases and the production of ettringite increases;CFB consumes the content of H⁺and free water in the liquid phase of MPC system.?4?The addition of CFB effectively improves the early interfacial flexural strength and bond pull-out strength of MPC repairing mortar;reduces the submerged flexural strength and bond pull-out strength of MPC repairing mortar;under freeze-thaw cycle,when the CFB content is 5%¹0%,the retention rate of interfacial flexural strength and bond pull-out strength of MPC repairing mortar are higher.?5?Under the standard curing conditions,the drying shrinkage of MPC repair mortar is significantly reduced by adding CFB,which has a better effect of compensating shrinkage.It is suggested that the optimum dosage of circulating fluidized bed ash in MPC system should be controlled at about 10%by synthesizing a number of performance indicators.